Set in 1952 in Saigon, Vietnam, toward the end of the French war against the Democratic Republic of Vietnam (1945-1954), on one level The Quiet American is a love story about the triangle that develops between Thomas Fowler, a British journalist in his fifties; a young American idealist, supposedly an aid worker, named Alden Pyle; and Phuong, a Vietnamese woman. On another level it is also about the growing American involvement that led to the full-scale American war in Vietnam.
In 1930 marked by growing anti-colonial unrest, Éliane Devries (Catherine Deneuve), a single woman born to French parents in colonial Indochina, runs her and her widowed father's (Henri Marteau) large rubber plantation with many indentured laborers, whom she casually refers to as her coolies, and divides her days between her homes at the plantation and outside Saigon. After her best friends from the Nguyễn Dynasty die in a plane crash, she adopts their five-year-old daughter Camille (Ba Hoang, as child). Guy Asselin (Jean Yanne), the head of the French security services in Indochina, courts Éliane, but she rejects him and raises Camille alone giving her the education of a privileged European through her teens.
The film begins in North Africa where large numbers of indigènes (French Algerian Tirailleurs as well as Tunisian or Moroccan Goumiers) have been recruited into the French First Army of the Free French Forces, that has been formed to liberate France of the Nazi occupation in World War II.
In 1911, a willful and determined man from peasant stock named Charles Saganne (Gérard Depardieu) enlists in the military and is assigned to the Sahara Desert under the aristocratic Colonel Dubreuilh (Philippe Noiret). Saganne attracts the attentions of Madeleine (Sophie Marceau), the daughter of the regional administrator. In the Sahara, Saganne earns the respect of the Arabs, including Amajan, an independent warrior. After several campaigns, Saganne travels to Paris on a diplomatic mission. After having an affair with a journalist in Paris, Saganne returns to Africa, where he leads a valliant defense against Sultan Omar. He is awarded the Grand Cross of the Legion of Honour, and marries Madeleine. The onset of World War I puts his success and happiness at risk.
Madame Emery and her beautiful 17-year-old daughter Geneviève (Deneuve) sell umbrellas at their tiny (and financially struggling) boutique in the coastal town of Cherbourg in Normandy, France, in the late 1950s. Guy (Castelnuovo), is a handsome young auto mechanic who lives with, and cares for, his sickly aunt, godmother Elise. Guy and Geneviève are deeply in love; they want to get married, and they want to name their first child "Francoise". Madeleine (Ellen Farner) is the quiet, shy, dedicated young caregiver who looks after Guy's aunt; Madeleine also has feelings for Guy, but has not expressed this. Suddenly Guy is drafted and must leave to become a soldier in the Algerian War. The night before Guy leaves, he and Geneviève pledge their undying love. Then they make love (apparently for the first time) and the very next day, Guy leaves.
En 1954 à Alger, le Front de libération nationale (FLN) diffuse son premier communiqué : son but est l'indépendance nationale vis-à-vis de la France, et la restauration de l'État algérien. Ali la Pointe propose des parties de bonneteau. Repéré par la police, il s'enfuit mais se fait agresser par un passant, il réplique et se fait tabasser par le reste du groupe. Rattrapé par la police, il se fait arrêter. Emprisonné, il assiste par la fenêtre de sa cellule à l'exécution d'une peine de mort par guillotine sur un nationaliste. Le FLN le contacte.
En 1954, au début de la guerre d'Algérie, deux hommes, que tout oppose, sont contraints de fuir à travers les crêtes de l’Atlas saharien d'Algérie. Au cœur d’un hiver glacial, Daru, instituteur reclus, doit escorter Mohamed, un paysan accusé du meurtre de son cousin. Poursuivis par des villageois réclamant la loi du sang et par des colons revanchards, les deux hommes se révoltent. Ensemble, ils vont lutter pour retrouver leur liberté.
L'histoire de huit journées de guerre. En mai 1954, durant la guerre d'Indochine, la 317e section locale supplétive composée de quatre Français et de quarante-et-un Laotiens reçoit l'ordre d'abandonner le petit poste isolé de Luong Ba à la frontière du Laos, pour rallier une colonne partie au secours du camp retranché de Diên Biên Phu.
Sergeant Brock (Gene Barry) and Goldie (Nat King Cole) are American Korean War veterans now serving as French Foreign Legion mercenaries in the First Indochina War. Angie Dickinson plays Brock's wife, a "half caste" Chinese Eurasian named "Lucky Legs" who resorts to smuggling to feed her five-year-old son she had with Brock. Brock abandoned her and the child when it was born with Asian features, feeling a "half breed" would not be welcome in America; an attitude towards miscegenation prevalent (in some quarters) at the time. Lucky is recruited by the French high command to use her knowledge to guide a demolition squad of Legionnaires led by Brock to blow up a hidden Viet Minh ammunition dump on the border with Red China. In return for her services, Lucky is promised by the French that they will arrange for her son's evacuation to America.
During the Algerian War, Bruno Forestier lives in Geneva to escape the enlistment in France. Working for French intelligence, he is ordered to kill Palivoda, who is pro-FLN (National Liberation Front of Algeria), to prove he is not a double agent. Refusal and hesitation keep him from carrying out the assassination.
In 1962, René Vautier, together with some Algerian friends, organized an audiovisual formation center to encourage a "dialogue in images" between the two factions. A film was edited from that experience, but the French police partially destroyed it. The images that were saved represent an unprecedented historical document: They tell of the Algerian War and the history of the ALN (National Liberation Army), as well as showing life after the war and, particularly, the reconstruction of the cities and the countryside after the war of Independence.